A metal layer is etched in the prior art by applying photo-resist on the metal layer, exposing, developing, and ashing the photo-resist using a mask, and then etching the metal layer, where the photo-resist tends to peel off due to poor adhesion between the surface of the metal layer and the photo-resist, so that a pattern on the metal layer may be damaged if the metal layer is etched.
Accordingly, how to avoid the photo-resist applied to the surface of the metal layer from peeling off is a technical problem highly desirable to be addressed.